Relationship between antibiotic resistance and biofilm-forming capacity with RND efflux pumps expression in clinical Acinetobacter baumannii isolates

This study investigated the gene expression pattern of resistance-nodulation-division (RND) efflux pumps, in Acinetobacter baumannii isolates with a focus on their association with carbapenem resistance and biofilm formation ability. A collection of 102 A. baumannii isolates was evaluated for antibiotic susceptibility testing using an automated broth microdilution technique. The ability of these isolates to form biofilms was evaluated using a standardized protocol. The isolates were genotyped using the Multiple-Locus Variable number tandem repeat Analysis-8 (MLVA-8) method and the gene expression levels of the RND efflux pump genes were quantified by real-time PCR. Results showed widespread antibiotic resistance, with 85% of isolates classified as multidrug resistant. Genotyping results identified 32 different MLVA types organized into six clusters (A–F) and 17 unique genotypes. The majority of isolates demonstrated the ability to form biofilms, and an inverse relationship was observed between biofilm formation and carbapenem resistance. The expression of the adeB gene was significantly increased in carbapenem-non-susceptible A. baumannii isolates. In addition, the expression of the adeG gene was 2.08 times higher in isolates capable of forming moderate to strong biofilms compared to those forming weak biofilms. The novelty of this study is a new insight into the relationship between efflux pump expression, antibiotic resistance and biofilm formation in A. baumannii, as well as AdeABC overexpression in carbapenem-resistant isolates and AdeFGH overexpression in biofilm-forming strains, providing potential therapeutic targets. These findings suggest that targeting RND efflux pumps may be a promising strategy to control survival and antibiotic resistance of A. baumannii isolates through biofilm inhibition.